Group 7

Key Stage 4

Meaning

Group 7 elements, also known as Halogens on the Periodic Table are the elements which have 7 electrons in their outer shell.

Group 7 elements are shown in green at the right of the Periodic Table.

About the Halogens

The Halogens have similar chemical properties because they all have 7 electrons on their outer shell.

Halogens all produce ions with a -1 relative charge because they gain an electron in chemical reactions.

The Halogens in order from most reactive to least reactive are:

• Fluorine (F)
• Chlorine (Cl)
• Bromine (Br)
• Iodine (I)
• Astatine (At)

Chemical Properties

The reactivity of Halogens decreases as you go down the Periodic Table.

Halogens all react strongly as bleaching agents.

Halogens all produce acids when combined with Hydrogen.

Halogens are toxic to bacteria and are used in disinfectants.

In a chemical reaction an extra electron is added to the outer shell. The reactivity decreases as you go down the group because: The outer electrons are further away from the nucleus with each additional electron shell making the force of attraction weaker. This makes it less able to gain an extra electron. Even though the charge of the nucleus increases the outer electrons are shielded from most of the positive charge of the nucleus by electrons in the inner shells.

Physical Properties

The physical properties of Halogens changes significantly as you go down the Periodic Table:

• Fluorine - A yellow gas at room temperature.
• Chlorine - A green gas at room temperature.
• Bromine - A brown liquid at room temperature.
• Iodine - A purple solid at room temperature.
• Astatine -A dark purple solid at room temperature.

The density, melting point and boiling point all increase as you go down the Periodic Table.

References

AQA

Group 7 (halogens), pages 131-4, GCSE Combined Science Trilogy 1, Hodder, AQA

Group 7 (halogens), pages 44-5, 46, GCSE Chemistry; Student Book, Collins, AQA

Group 7, page 110, GCSE Combined Science; The Revision Guide, CGP, AQA

Group 7, page 25, GCSE Chemistry; The Revision Guide, CGP, AQA

Group 7, pages 16-18, GCSE Chemistry, Hodder, AQA

Group 7, pages 28-29, 31, GCSE Chemistry; Third Edition, Oxford University Press, AQA

Group 7, pages 61-63, GCSE Chemistry, CGP, AQA

Group 7, pages 61-63, GCSE Combined Science Trilogy; Chemistry, CGP, AQA

Halogens, page 110, GCSE Combined Science; The Revision Guide, CGP, AQA

Halogens, pages 131-4, GCSE Combined Science Trilogy 1, Hodder, AQA

Halogens, pages 16-18, GCSE Chemistry, Hodder, AQA

Halogens, pages 25, 79, GCSE Chemistry; The Revision Guide, CGP, AQA

Halogens, pages 28-29, 31, 158, 188-189, GCSE Chemistry; Third Edition, Oxford University Press, AQA

Halogens, pages 44-5, 46, GCSE Chemistry; Student Book, Collins, AQA

Halogens, pages 61-63, GCSE Chemistry, CGP, AQA

Halogens, pages 61-63, GCSE Combined Science Trilogy; Chemistry, CGP, AQA

Halogens; reaction with alkenes, pages 178-9, GCSE Chemistry, Hodder, AQA

Edexcel

Group 7, pages 20, 74, 75, GCSE Chemistry; The Revision Guide, CGP, Edexcel

Group 7, pages 40, 49, 213-215, GCSE Chemistry, CGP, Edexcel

Group 7, pages 83, 124, 125, GCSE Combined Science; The Revision Guide, CGP, Edexcel